Bulugh al-Maram, Book 6, Hadith 735 (English)

Ibn ’Abbas (RAA) narrated, ‘A woman from the tribe of Juhainah came to the Prophet and said, ‘My mother had vowed to perform Hajj, but she died before fulfilling her vow. Should I perform Hajj on her behalf? The Prophet said: "Yes perform Hajj on her behalf. Had there been a debt on your mother, would you have paid it or not? So, pay off her debt to Allah, for He is most deserving of settlement of His debt." Related by Al-Bukhari.

وَعَنْهُ: { أَنَّ اِمْرَأَةً مِنْ جُهَيْنَةَ جَاءَتْ إِلَى اَلنَّبِيِّ ‏- صلى الله عليه وسلم ‏-فَقَالَتْ: إِنَّ أُمِّي نَذَرَتْ أَنْ تَحُجَّ, فَلَمْ تَحُجَّ حَتَّى مَاتَتْ, أَفَأَحُجُّ عَنْهَا? قَالَ: " نَعَمْ " , حُجِّي عَنْهَا, أَرَأَيْتِ لَوْ 1‏ كَانَ عَلَى أُمِّكِ دَيْنٌ, أَكُنْتِ قَاضِيَتَهُ? اِقْضُوا اَللَّهَ, فَاَللَّهُ أَحَقُّ بِالْوَفَاءِ } رَوَاهُ اَلْبُخَارِيُّ 2‏.‏ ‏1 ‏- كذا هو في الأصل، وفي " الصحيح " والمطبوع، والشرح.‏ وتحرف في " أ " إلى: " إن ".‏‏2 ‏- صحيح.‏ رواه البخاري ( 1852 )‏.‏

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also referenced under: Book 6, Hadith 9 (In-Book)